The invention relates to non-return valves; it relates, more particularly, to such valve provided with a reverse flow capacity under controlled conditions of adverse pressure differential.
Non-return valves employing elastically deformable membranes are known in the art. Such valves are commonly employed in circumstances where purely unidirectional flow conditions are to be governed, such as the discharge valves of positive displacement air compressors. Typically, a flat metallic spring is arranged to be preloaded agains the periphery of an orifice cut into a backing plate, with the spring secured to the backing plate along one edge. When the pressure below the orifice exceeds that equivalent to the preload, the spring deflects away from the seat and allows flow, when the pressure differential is opposite, flow is interdicted.
In many circumstances, of which the inflation of tires and other inflatable pneumatic artifacts is only one example, it is highly desirable to provide a non-return valve which acts in a uni-directional manner during the actual inflation process but which also permits reverse flow should it occur that the inflation pressure exceeded that desired for safe operation. Such circumstances frequently occur during the mounting of tires on their rims; the installer, desirous of ensuring a proper seating of the tire beads against the rim, inflates the tire to the maximum available in his pressure line. Since this pressure is commonly much greater than the permissible inflation pressure, it is not uncommon that the tire, or the rim, disintegrate in the course of this procedure.
Not only is this condition wasteful, it is also dangerous. In some instances -- commanded by the General Industry Safety Orders of the State of California, for example -- inflation of high-pressure (commonly truck) tires takes place in a metal cage, so that flying fragments may be safely retained.
Such accidents can be, however, much more readily prevented by the provision of a valve which would automatically relieve excessive pressures, during, or immediately after, the inflation process.
Such valves, permitting flow in either direction in the presence of appropriate pressure differentials, can also find application in control systems based on the manipulation of hydraulic or pneumatic pressure in a circuit; such function can be developed by the use of two conventional relief valves acting in opposition, but it would be of great benefit to be able to use a single component to achieve the desired end.
It is, therefore, the primary object of the invention to teach the construction of a two-way relief valve.
It is also an object of the invention to provide a charging valve for inflatable artifacts which is capable of relieving excess inflation pressure and reliably seal the artifact upon the attainment of the desired pressure level.
It is also an object of the invention to provide a flow control valve capable of differential action which is simple in construction and reliable in use; and in which the principal control element is a tubular, elastically-deformable membrane coacting with a circumferential sealing edge on a disk.